What's The Difference Between Sofa Bed Mattresses & Sleeper Sofa Mattresses?

There is no technical definition of "sofa bed" or sleeper sofa". Therefore a sofa bed mattress can be called a sleeper sofa mattress. Nevertheless, there is a commonly understood meaning fdor each of the terms.

A sofa bed is a couch which unfolds into a bed in three sections. As such there is a complex mechanism wherein the the mattress folds into three sections and the top section tucks up into the back of the sofa.

A sleeper sofa is a couch which unfolds into two pieces. Such a ubit is much simpler, cheaper unit, but has very limited utility as a sofa